In a long term evolution (LTE) system which has been spotlighted as the next-generation mobile communication standard, various scheduling methods which assign radio resources for transmitting/receiving data and configure various types of transmission parameters have been suggested. Among them, four representative scheduling methods are as follows.
First, a dynamic scheduling method basically requires downlink (DL) scheduling information or uplink (UL) scheduling information for each data transmitted in a transmission time interval (TTI).
If a terminal and a base station are operated by an asynchronous HARQ method in order to transmit or receive data, in the dynamic scheduling method, the DL assignment or the UL scheduling information is required at the time of initial transmission or retransmission of data. In contrast, if the terminal and the base station are operated by a synchronous HARQ method, the DL assignment or the UL scheduling information is required for each data at the time of the initial transmission of the data, but is not required at the time of the retransmission of the data. At this time, the DL assignment or the UL scheduling information in the dynamic scheduling method is available in a single terminal.
Second, in a persistent scheduling method, the DL assignment or the UL scheduling information is not transmitted in the TTI unlike the dynamic scheduling method, and the base station statically informs a terminal of a data transmitting/receiving method through a radio resource control (RRC) signal in advance, similar to the configuration of a radio bearer. Accordingly, the terminal uses predetermined information through the RRC signal at the time of the transmission/reception of the data, without the DL assignment or the UL scheduling information.
For example, when the base station configures a radio resource A, in which downlink data with a transmission format B is received in a cycle C, in the terminal through the RRC signal in advance, the terminal can receive the data using the values A, B and C, without the DL assignment. Similarly, even when the terminal transmits data to the base station, the data can be transmitted according to the information without separate UL scheduling information.
Third, a grouping scheduling method is similar to the dynamic scheduling method. However, while the dynamic scheduling method is available in a single terminal, the grouping scheduling method is available in a plurality of terminals.
For example, if first to tenth terminals are included in a group A and first, second and third terminals request DL assignment, the base station includes a group identifier A, identifiers of the first, second and third terminals and the DL assignment of the terminals in group DL assignment and transmits the group DL assignment.
Fourth, a synchronous HARQ retransmission or semi-static scheduling method is used when the terminal and the base station transmit/receive data by an asynchronous HARQ method. In this method, the terminal and the bas station are operated by the asynchronous HARQ method at the time of initial transmission of data and are operated by the synchronous HARQ method at the time of retransmission of data.
For example, in a case where the HARQ transmission method is configured in the terminal, the terminal and the base station are operated by the synchronous HARQ method when the retransmission is performed, although the asynchronous HARQ information is included in the DL assignment. That is, the information such as a retransmission cycle is previously configured in the terminal through the RRC signal and the retransmission is performed using the configuration information and the DL assignment acquired at the time of the initial reception of data.